The aviation industry is investing in innovative fuel concepts that may provide environmental benefits. While some of them are already being produced and used regularly in aircraft operations, (e.g. Sustainable Aviation Fuels), others are still under research and development, such as Lower Carbon Aviation Fuels and Hydrogen.
Sustainable Aviation Fuels
Annex 16 Volume IV defines a "CORSIA sustainable aviation fuel" as a "renewable or waste-derived aviation fuel that meets the CORSIA Sustainability Criteria under this Volume." Sustainable Aviation Fuels (SAF) are a reality, as can be seen by the various conversion processes and feedstocks available to produce SAF, and the large number (over 200,000 flights) commercial flights that have been flown with SAF. Extensive information on ICAO initiatives on SAF is provided here.
Lower carbon Aviation Fuels (LCAF)
Annex 16 Volume IV also brings the concept of "CORSIA lower carbon aviation fuel", defined as "a fossil-based aviation fuel that meets the CORSIA Sustainability Criteria under this Volume". Research is ongoing on possible technologies that may allow the production of fossil fuels with a smaller carbon footprint, such as Carbon Capture, Utilization and Storage (CCUS) and the use of renewable energy in oil refineries. More detailed information on the LCAF technologies were provided during the ICAO Stocktaking Seminar 2019. ICAO is closely following the evolution of such technologies and investigating the development of proper methodologies to assess their potential environmental benefits. More information on this work can be found here.
Looking to the future, it should be noted that both definitions of "CORSIA sustainable aviation fuels" and "CORSIA lower carbon fuels" are not restricted to liquid fuels such as jet-A1. In that regard, research is ongoing to evaluate hydrogen as a possible aviation fuel in the future. To date, several factors still hinder a possible use of hydrogen in commercial ﬂights, such as on-board storage, safety concerns, the high cost of producing the fuel and the need for dedicated infrastructure at airports. Research projects are ongoing to demonstrate the feasibility of hydrogen propulsion and to overcome these challenges, in support of longer term environmental objectives for civil aviation.
More details on the state of play with regard to Hydrogen fuel can be found on the Environmental Report 2019 (Chapter 4 - Electric, Hybrid, and Hydrogen Aircraft – State of Play).